1. Field of the Invention
This invention relates to a digital signal recording apparatus for recording an input signal on a recording medium in the form of a pulse train recording.
2. Description of the Prior Art
Up to now, various signal recording apparatus for recording signals on a recording medium by a rotating magnetic head have been investigated and put into practice. In video tape recorders (VTRs), for example, signals are recorded obliquely on a magnetic tape by plural recording magnetic heads provided at predetermined positions on a rotating drum.
When editing is necessary, an erasing magnetic head, positioned on a rotary drum at a location preceding the position of a recording magnetic head in the direction of rotation, traces the recording track. Signal re-recording is performed by the recording magnetic head after a flying erasure operation is performed by the erasure magnetic head for a period corresponding to the re-recording period. In a digital VTR for digital recording of video signals, the flying erasure operation is also occasionally performed for satisfactory signal re-recording during the editing. In this type of the signal recording apparatus, a separate erasure control circuit for supplying the electrical current to the erasure magnetic head in timed coordination with the re-recording period or the transmitting control signals is necessary. In addition, the power consumption is increased.
In the currently practiced digital VTRs, as shown for example in the Japanese Unexamined Patent Publication No. 36312/1984, the recording magnetic head and the erasure magnetic head are provided in proximity to each other. Control means for commonly controlling the operational timing of each of these magnetic heads is realized by a simplified circuit having a high power efficiency so as to overcome the above described inconveniences.
To perform an editing operation in such a signal recording apparatus, an erasure magnetic head is provided to the rotary drum. The recording track is erased by a flying erasure operation of the erasure magnetic head to effect satisfactory signal recording. When such a flying erasure operation is performed, a separate erasure control circuit is used for supplying the current to the erasure magnetic head in timed coordination with the re-recording period. In addition, a rotary transformer for transmitting the erasure control signals is necessary. As a result, in the digital VTRs shown in the above publication, distortions common to magnetic recording, such as peak shifts, are produced as a result of the non-return to zero (NRZ) recording. Thus, a circuit is needed to compensate for the distortions. Moreover, an adjustment operation is necessary at five to six points for each channel to provide a circuit constant for the compensation circuit.